When my phone is in car mode the battery gets pretty hot, up around 110 degrees. It doesn't get much hotter than that so I am not over concerned. I have tried my regular app, Car Ultra, and the stock app. I have the app setup to turn on when Bluetooth is connected and the charging status changes. I have the charger plugged in to indicate the charging status change. The app does not let the screen turn off when plugged in and running. My droid 2 did the same thing. Does the battery just heat up due to all the information running? Bluetooth, GPS, screen staying on? Any thoughts?